Improved anti-wear lubricating composition



United States Patent 3,108,961 IMPRQVED ANN-WEAR LUBRICATITQG COMPUSITEON Frederick T. Finnigan and Paul E. Pfeifer, Crystal Lake,

111., assignors to The Pure Oil Company, Chicago, 111.,

a corporation of Ghio No Draw'mg. Filed Dec. 21, 1959, Ser- No. 850,736

3 Claims. (Cl. 252-33.4)

This invention relates to a mineral oil composition for use as a crankcase oil in the lubrication of automobile engines. More particularly, this inventionrelates to a superior additive combination for crankcase oils, comprising a dialkyl phthalate and a triaryl ip'hosphtitqlto enhance their anti-wear properties. 1

According to this invention, we have found that the combination of a dialkyl phthalate and a triaryl phosphate in mineral lubricatingoilcompositions exhibits synergistic anti-Wear properties. We have found that betiveen about 1.80 and '2.5 .wt. 'percent of the foregoing combination of additive, particularly the combination of dibutyl phthalate and tricresyl phosphate, when used in a detergent-containing oil, gives anti-scuffing and antiwear properties beyond that of either addend used alone. At least about 1.0% of each addend, and not in excess of about 2.5% of the combination of addends, should be used for maximum effectiveness.

The modern automobile engine is a high-output, higheiiiciency, compact machine, generally of the overheadvalve type, which places a considerable demand on engine lubricating oils because of the multifunctional requirements necessary for good performance. These engines employ a plurality of closely-fitting metallic surfaces in direct, high-speed, moving contact with other metal parts. Accordingly, lubrication to protect against wear becomes the primary requirement of the oil in order that the en gine parts, some of which are under extreme pressure, can be maintained in reasonably good operating condition. Such mechanical elements of the engine as piston rings and cylinder walls, and the component parts of the valve train, such as cam-shaft lobes, cam followers or hydraulic valve-lifters, rocker-arm shafts and bearings, oil-pump distributor drive-gear, and the like, have small clearances between the cooperating parts of the mechanical combination in which these elements are used. Increased unit loading of such elements as the cam-shaft, valve lifters, and rocker-arm mechanism inherent in the a compact design of the engine, coupled with a variety of geometric shapes and metallurgy of valve trains in various engines, have created unique wear problems. A particularly difiicult problem is the scufiing, spalling, and wear of lifter and cam-shaft lobes. The spalling of the lifter appears to be the result of fatigue of a thin layer of metal on the face of the lifter, causing bits of metal to be lost from the surface. Other failures occure because of high wear, with the wearing surfaces being worn smooth; Results of wear vary from noisy operation, .due to loss of the original geometry of cam or mating lifter surfaces, to complete removal of cam lobes and resulting engine malfunction.

Although a large number of test procedures have been developed to investigate these phenomena, problems arise in such studies and evaluations because of the difficulties encountered in measuring the specific properties involved. No standardized method of measuring lubricating prop erties directly has been established by the American Society for Testing Materials. The only satisfactory manner in which the anti-wear characteristics of a lubricating oil can be determined is to actually test the oil under service conditions in the crankcase of an automobile engine. It is only since the advent of the high-output,

3,1083% 1 Patented. Oct. 29, 1 963 ice high-'efiiciency automobile engine that attention has been directed to specific anti-wear properties of lubricating oils. Although a number of various agents have been developed, and it is known that such agents are helpful when conditions of boundary lubrication are met, the use of such materials doesnot necessarily meet the unique lubrication requirements of the modern engine valve train. Furthermore, sludge and varnish deposits resulting from the oxidation of lubricating oils and the products of fuel combustion have a tendency to prevent the free fiow of oil in the lubricating system of the engine which includes smml passage-Ways and oil holes to areas requiring lubrication. For this purpose, deter-gents are normally included in modern lubricating oil formulations to reduce the tendency of varnish and sludge deposits to adhere to passage-ways, areas behind the piston rings, or to the crankcase. Crankcase oils are formulated so that the detergency capacity or level is sufficient to mitigate the agglomeration and deposition of soot, dirt, and oxidation products under normal operating conditions, and between oil changes. However, it is known that at these highdetergency levels, the detergents themselves have a deleterious effect on the anti-Wear characteristics of the oil.

The amount of detergent added is, in general, the approximate amount necessary to pass the detergency requirements of the MlLL 2104A military specification test, but higher or lower amounts may be present, de-

ending upon the engine characteristics, base oil, and so forth. In this test, the effect of engine oil on ring sticking, wear, and accumulation of deposits is determined using the Coordinating Research Council L1545 test procedure. This procedure is described in CRC Handbook, Coordinating Research Council, lno, 1946. In essence, this test'consists of operating a special, onecylinder diesel engine on a straight-run fuel which must conform to a number'of requirements. A minimum sulfur content of 0.35 wt. percent is required. This level of detergency will hereinafter be referred to as a high level of detergency.

The inimical influence ofa high detergency level on wear characteristics is illustrated by the following data which were obtained using the MS Sequence IV test, here inafter described in detail:

2 A proprietary combination detergent for lubricating oils consisting of a barium alkyl phenol sulfide having admixed therewith a calcium petroleum sulfonate.

3 Severe failure of 34 cams and lifters prevented completion of test; thus a 24-hour average wear of the uudistresscd units could not be determined. If it were possible to run the test after the first failures occurred, it is expected that all or nearly all cams and lifters would be severely scuffed, with average wear values of at least 0.125.

'In accordance with this invent-ion, we have found that the foregoing "difficulty can be overcome by providing an additive mixture comprising a detergent and a combination of antiwear agents comprising a dialkyl phthalate, such as dibutyl phthalate, and a triaryl phosphate, such as tricresyl phosphate.

. 2,346,154, 2,369,632, 2,420,893, and others.

It is an object of this invention to provide an engine- :lubricating oil composition which has excellent anti-wear and rust-inhibiting characteristics comprising the combination of a detergent and dibutyl phthalate and tricresyl phosphate.

Another object of this invention is. the formulation of an engine-lubricating oil composition which substantially reduces the sticking of hydraulic valve-lifters, and the wear of hydraulic valve-lifters, piston-ring wear, piston-ring sticking, and especially under low-temperature conditions, the wear of cam followers and cam-shaft lobes, and avoids filling piston-ring grooves with sludge and varnish deposits.

These and other objects of the invention be made more apparent from the following detailed discussion of the instant invention.

A high level of detergency in a lubricating oil is provided by adding thereto suflicient amounts of a detergent selected from a group of compounds which will keep oilinsoluble matter, such as oil-oxidation products, dirt, fuel, soot, resins, and so forth, in suspension so that they will not settle out or adhere to metal surfaces and build up a sludge or varnish deposit. Various types of detergents may be used including, but not limited to, petroleum sulfonate or synthetic sulfonate salts, where the cationic substituent of the sulfonate is an alkali metal, alkaline-earth metal, aluminum, tin, lead, and so .fiorth. Examples are calcium petroleum sulfonate; basic barium salt of wax-substituted naphthalene sulfonate; sodium keryl benzene sulfonate; alkaline-earth metal :alkyl phenolsulfides, e.g., barium amyl-phenolsulfide, barium isoamylphenol sulfide, basic barium dibutylpheno lsulfide, calcium octylphenoldisulfide, calcium dicetylphenolsulfide, and aluminum dicetylphenolsuhfide; and the metal salts of wax-substituted phenol derivatives which are rather complex molecules prepared by attaching one or more long-chain, paraffinwax molecules to a hydroxyaromatic ring nucleus, which then may be carboxylated. From the last, the normal or basic metal salt is formed by attachment to the hydroxyl or the carboxyl group.

Examples of suitable phenates and metal salts of waxsubstituted phenol derivatives are disclosed in US. Patent 2,197,833, and others. Metal salts of phosphorus derivatives may also be used as detergent components of the subject composition. Alkaline-earth metal derivatives of phosphorus-sulfide-treated, high-molecular-weight, saturated, or unsaturated esters, such as lard oil, sperm oil, degras, and so forth, exhibit deter-gent properties and may also be used.

Combinations of two or more detergents may be used where the detergency action of some of the species is limited. For example, a detergent combination is illustrated by an alkaline-earth metal alkylphenolsulfide-pertroleurn sulfonate combination, as for example, barium lubricating oil. The instant invention is directed to overcoming this effect in compounded lubricating oils when amounts of detergent which have a detrimental influence on the anti-wear characteristics are employed in the composition. In general, between about 2 to 8% by wt. of the detergent may be used with the anti-wear combination of dialkyl phthalates and triaryl phosphates of this invention. In some instances, it may be desirable to employ amounts outside this range.

The anti-wear agents to be employed in "lubricating-oil compositions in accordance with this invention to overcome the depreciation in anti-wear due to the high level of detergency of the lubricating oils consist essentially of combinations of oil-soluble dialkyl phthalates and oil-- soluble triaryl phosphates. Examples of dialkyl phthalates coming within the definition of this invention are dimethyl ph-thalate, dibutyl phthalate, dicyclohexyl phthalate, dihexyl phthalate, di-Z-ethylhexyl phthal-ate, diisodecylphthalate, amylhexyl phthalate, amylpropyl phthalate, butyl isodecyl phthal-ate, propylhexyl phthalate, isooctyl isodecyl phtha-lalte, propy lbutyl phthalate, butyl octyl phthalate, butyl cyclohexyl phthalate, and n-octyl n-decyl phthalate. The triaryl phosphates include cresyl diphenyl phosphate, phenyl dinaphthyl phosphate, tripheny'l phosphate, trinaphthyl phosphate, and tricresyl phosphate. f

In order to demonstrate the invention, a series of valve litter and camwear tests was made in a 1959 DeSoto engine, using as a lubricant a commercial crankcase oil formulation containing dibutyl phthalate, tricresyl phosphate, and combinations thereof in various concentrations. The commercial formulations used in these tests consisted of base oil refined by current methods and blended to meet SAE 10W. viscosity specifications, containing 53 vol. percent of a proprietary additive consisting of the barium salt of amyl phenol sulfide and alkaline calcium petroleum sulfonate in equal proportions, and about 20% of mineral oil. detergent additive is characterized by the following composition and properties; 6.53% barium, 1.40% calcium, 3.17% sulfur, 15.9% ash as sulfate, and a specific gravity 60 F.) of 1.02.

The test procedure used as a standardized test method known in industry as MS Test Sequence IV. This test method is described in detail in a report of Section G-IV of Technical Committee B of ASTM Committee 13-2, dated 10/6/59, and is specifically designed to define the anti-scuffing and anti-wear properties of oils under high-speed and high-temperature operating conditions. The test engine is set up with the valve springs overloaded by 36%, and each test is run with a new cam shaft and new hydraulic valve lifters or cam followers. The specified test period is 24 hours, made up of six 2-hour running periods and six 2-hour shutdown periods. The

55 tests are terminated prior to 24 hours when a serious cam amy-lphenolsulfide-calcium petroleum sulfonate. Other or lifter failure occurs.

TABLE II MS Test Sequence IV Data Run No 1 2 a 4 s e 7 s 9 10 11 12 13 Percent DBP 0 0 1.0 2.0 2. 5 2.5 0 0 0 1.0 1.0 1.0 1.0 Percent TOP 0 0. 0 0. 0 0. 0 0. 0 1. 5 2. 5 2. 5 0. 1. 5 1. 5 1. 5 Test Hours Completed 1 2.0 24 24 24 24 24 24 24 24 24 24 24 Average Litter Wear- 1.3 1.9 0.6 2.4 1. 5 4. 5 1.4 3. 9 O. 2 1.8 1. 2 Average Cam Wear 8. 3 2. 7 3. 8 3. 9 0.3 4. 8 3. 9 3. 8 1. 4 0 0 Average Combined Cam and Litter Wear. a. 6 4. e 3. 9 6. 3 1. s 9. 3 5. 3 7. 1. e 1. 8 1. 2 Distressed Cains or Lifters 1 3 7 1 0 0 3 0 0 2 0 0 0 1 Distressed cams or lifters are those which have suffered scufiing and higherthan-average wear.

These valuesare excluded from average wear computations. This distress was so great in runs 1 and 2 that the engine could no longer be run after 2 hours.

As seen from the table, runs 1 and 2 without antiwear components resulted in severe failure of at least 3 littercam combinations during the first two hours of the test.

. If these tests could have been run to complete the 24- hour period, complete failure of all ornearly all of the deleterious efiect ion the anti-wear characteristics of the 75 16 cams and lifters would be expected. The wear figures shown are average lifter wear, average cam wear, and average combined lifter and cam wear, all shown in inches x for cam-lifter combinations in which neither member was distressed. If either the cam lobe or lifter, or both, suffered wear significantly greater than the average, the combination was counted as one distressed unit and the wear values were not included in the average. Runs 3, 4, 5, and 6 show that from 1 to 2 of dibutyl phthalate, although giving suflicient wear protection to run the total of 24 hour test period, gave both a high average-wear and a high number of distressed cams or lifters. Runs 7, 8 and 9 show that between 1 and 2 /2% of tricresyl phosphate also permitted running for the 24-hour test period, but again gave average wear values which where too high, and produced too many distressed cams or lifters. In runs 10, 11, 12 and 13, the combination of dibutyl phthalate and tricresyl phosphate is shown. Here, not only is the average wear reduced, but the number of distressed cams or lifters has been brought to substantially zero.

In formulating a crankcase oil having a high level of detergency in accordance with the teachings of this invention, about 2 to 8% by weight of detergent, based on total motor oil composition is preferred. This detergent is preferably of the barium type containing the salt of an alkyl phenol slufide and alkaline calcium petroleum sulfonate. The optimum amount of detergent used may be determined experimentally. In general, amounts in the preferred range will be eifective, out amounts outside this range may in some cases be necessary.

The amount of dialkyl phthalate and triaryl phosphate to be -used in accordance with this invention when incorporated as a combination is between about 1.80 and 2.5 wt. percent based on the mineral lubricating oil comketed by Union Carbide and Carbon under the mark Ucon, and the esters of dibasic acids, such as di-2- ethylhexyl sebacate. It is to be observed that the particular oleaginous lubricant or base oil employed in making the blends of this invention is not considered critical.

The compositions of this invention are especially adapted for use in so-called multigraded oils which are crankcase lubricants satisfying the requirement of a range of SAE viscosity characteristics. Other addends may be used to impart beneficial properties to the lubricating-oil composition of this invention. For example, various viscosity-index improvers, pour-point depressants, anti-foam agents, oxidation inhibitors, rust inhibitors, and the like, may be used. Examples of viscosity-index improvers which may be used include high-molecular-weight polymeric esters (10,000-15,000) of methacrylic acid and higher fatty alcohols, e.g., lauryl, cetyl and octyl alcohols, having a viscosity of 23,000 SUS at 100 F., and polymeric esters (l0,00020,000) of methacrylic acid and higher fatty alcohols, e. g., lauryl, cetyl, and octyl alcohols, having a viscosity of 43,000 SUS at 100 F. and a viscosity of 3,700 SUS at 210 F. The foregoing compositions act as pour-point depressants and viscosity-index improvers.

Table III gives additional examples of high-detergency lubricating-oil compositions coming within the scope of this invention, using particular combinations of solventrefined oils and diiferent amounts of addends. In this invention, the term phthalates is intended to include ortho-, meta-, and para-phthalates, and it is also intended that an alkyl-substituted aryl phosphate includes isomers, such as the ortho, meta, and para isomers in the case of a benzene ring, with respect to the position of the alkyl substituent in relation to the point of attachment of the phosphate radical to the aromatic ring.

TABLE III SAE Grade Oil 5W-20 10W-30 10 10W Proportions, percent by weight MCSR Neutral, 170 SUS 100 F r- 10.0 10.0 10.0 87. 4 87. 4 87. 4 87. 4 MO SR Neutral 85 SUS 100 F 77. 7 77.7 77.7 74. 9 74. 9 74. 9 74. 7 74. 7 MC SR Bright Stock 150 SUS 210 F 22.0 22.0 22.0 22.0 22.0 Detergent 2. 5 10 9.0 0.5 Ba-amylphenolsulfide with (la-petroleum sulionate 2. 5 4. 5 9. 0 0. 5 0. 5 Ba-isobutylphenolsulfide with (la-petroleum sulionate 2. 5 4. 5 Dialkyl phthalate 1.0 1. 5 1.0 1. 2 Dibutyl phthalate 1.0 1. 0 0. 5 1. 2 1. 2 Dihexyl phthalate 1.0 l. 0 0.5 1.4 'Iriaryl phosphate 1.0 1. 0 1. 5 1. 3 Tricresyl phosphate 1.0 1. 5 1.0 1. 2 1. 3 Oresyl diphenyl phosphate 1. 0 1. 5 0. 5 1. 0 Pour-Point Depressant and VI Improven 7. 8 0.1 0.1 0.8 Acryloid 710 7. 8 7. 8 1.1 1. 1 1.1 0.2 0.2 0.8

position. As a minimum, at least about 1.0% of each of these addends is used and not in excess of about 2.5% of the combination.

The oleaginous lubricating constituent of the blend may be any solvent-refined or conventionally-refined hydrocarbon oil, or lubricating oil or fraction thereof, derived from petroleum oils produced from a Pennsylvania, Mid- Continent, or Coastal crude, or other source. Viscosity requirements of the finished lubricating-oil blend dictate the composition of the base oil used and blends may be prepared from a single fraction or an admixture of several lubricating-oil fractions may be employed to take advantage of the well-known blending phenomena and properties of each. In addition, various amounts of solvent extracts obtained in the solvent refining of lubricatingoil fractions may also be employed in preparing the mineral oil base. Various synthetic oils, which may also lack sufiicient anti-wear qualities, may be used as the oleaginous constituent of the blend. Examples of these lubricants include polyalkylene glycols, such as those mar- The invention has been described in relation to a number of non-limiting examples showing compounded motor oil compositions that are especially elfective in reducing wear and friction in an internal combustion engine,

particularly in the valve-train assembly. Other mineral oil compositions can be compounded than those disclosed herein using the instant invention, and such modifications are within the scope of the invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A motor oil composition consisting essentially of a major portion of a mineral lubricating oil, about 2 to 8% by weight of a combination detergent comprising the (barium salt of amyl phenol sulfide and alkaline calcium 7 petroleum sulfonate sufiicie nt to suspend oil-insoluble a major portion of a mineral lubricating oil, about 2 to 8% by weight of a combination detergent comprising the barium salt of amyl phenol sulfide and alkaline calcium petroleum sulfonate suflicient to suspend oil-insoluble materials and produce a depreciation in anti-wear characteristics of said composition, about 1.0% by Weight of di butyl phthailate and about 1.0 to 1.5% by weight of trioresyl phosphate.

3. A motor 'oil composition consisting essentially of a major portion of a mineral lubricating oil, about 2 to 8% by Weight of a combination detergent comprising the barium salt of army] phenol sulfide and alkaline calcium petroleum sulfonate suflicient to suspend insoluble materials and produce a depreciation in anti-wear chairacteristies of said composition, about 1.0% by weight of 15 tricresyl phosphate and about 1.0 to 1.5 by Weight of dibutyl phthalate.

References Cited in the file of this patent UNITED STATES PATENTS 2,215,590 Maverick Sept. 24, 1940 2,796,400 Thornley June 18, 1957 2,839,469 Pfei-fer et al. June 17, 1958 FOREIGN PATENTS 446,567 Great Britain Apr. 27, 1936 699,103

Great Britain O'ct. 23, 1953 OTHER REFERENCES Davey: I. and E. Che/111., vol. 42, No. 9, September 1950, pp. 18414847 pertinent. 

1. A MOTOR OIL COMPOSITION CONSISTING ESSENTIALLY OF A MAJOR PORTION OF A MINERAL LUBRICATING OIL, ABOUT 2 TO 8% BY WEIGHT OF A COMBINATION DETERGENT COMPRISING THE BARIUM SALT OF AMYL PHENOL SULFIDE AND ALKALINE CALCIUM PETROLEUM SULFONATE SUFFICIENT TO SUSPEND OIL-INSOLUBLE MATERIALS AND PRODUCE A DEPRECIATION IN ANTI-WEAR CHARACTERISTICS OF SAID COMPOSITION, ABOUT 1.2% BY WEIGHT OF DIBUTYL PHTHALATE AND ABOUT 1.2% BY WEIGHT OF TRICRESYL PHOSPHATE. 